Overfishing is rapidly degrading the sustainability of coral reef fisheries in East Africa, especially in tropical coastal regions where small-scale fishers are seeing alarming declines in fish diversity and productivity. A groundbreaking study published in Sustainability and led by scientists from the Wildlife Conservation Society (WCS) and the University of Rhode Island reveals that targeting only fast-growing species is an ineffective approach to long-term fisheries management.
Key Findings: Loss of Fish Species is Undermining Coastal Food Security
The study highlights that traditional fisheries management strategies focused on resilient, fast-growing fish species fail to compensate for the disappearance of more vulnerable species, such as snappers, goatfish, unicornfish, sweetlips, and soldierfish. These fish, often caught in large schools, are essential for coastal diets due to their high nutritional value.
“Current catches are missing a significant portion of historically common species,” said Associate Professor Austin Humphries, co-author of the study. “This loss impacts both food security and the livelihoods of local fishing communities.”
Why Protecting Fish Diversity Matters More Than Targeting Resilient Species
The research team analyzed decades of data from seven marine protected areas, some closed to fishing for over 45 years. By comparing these no-take zones with local fishing grounds, scientists identified a clear decline in fish biomass and diversity outside protected areas.
Dr. Tim McClanahan, lead author and Director of Science at WCS Global Marine Program, explained:
“Nearly 50% of potential fisheries production is lost when once-abundant species disappear. Relying solely on resilient species gives a false sense of sustainability.”
This study challenges previous recommendations that encouraged fishers to focus on species thought to withstand fishing pressure. Instead, the data shows that total fish yield is highest when both resilient and vulnerable species coexist—especially those that school and contribute significantly to total catch volume.
Gear Restrictions and Community-Based Management Can Rebuild Fish Populations
Fishing methods matter. The study found that fishing gear like gillnets and spearguns disproportionately target schooling species, accelerating their decline. In contrast, regions with gear restrictions and managed access showed better recovery of fish communities and higher yields.
“Areas that regulate gillnets and spearguns see better outcomes for fish populations,” said Jesse Kosgei, a marine research scientist at WCS Kenya.
Limitations of Traditional Fisheries Sustainability Metrics
Conventional length-based assessments, often used to measure fisheries sustainability, fail to account for entire species disappearing from catches, rendering them ineffective in high-biodiversity areas like coral reefs.
Instead of using these limited tools, the researchers advocate for a holistic approach that monitors full fish community composition, not just a few target species.
Rethinking Coral Reef Fisheries Management: A Call to Action
This research provides a clear message: Sustainable coastal fisheries depend on protecting the full diversity of marine life, not just harvesting what remains. Overfishing of vulnerable, schooling species is reducing ecological resilience, food security, and the long-term viability of coastal economies.
Key Takeaways for Sustainable Coastal Fisheries:
- Overfishing is driving the loss of key fish species in East Africa.
- Focusing only on resilient species fails to sustain fisheries productivity.
- Gear restrictions can help rebuild diverse fish communities.
- Holistic, community-based management is critical for long-term sustainability.
By shifting focus from individual species to ecosystem-wide protection, policymakers and fishers can help reverse the damage and ensure a more secure future for marine biodiversity and coastal livelihoods.
Reference:
Timothy Rice McClanahan et al., Fisheries Sustainability Eroded by Lost Catch Proportionality in a Coral Reef Seascape, Sustainability (2025). DOI: 10.3390/su17062671
Provided by: Wildlife Conservation Society